Our research group proposes a continuation of studies of the biology and biochemistry of influenza viruses initiated in part in 1969. We shall continue the application of genetic methods to a definition of viral structure and function. Specifically, through genetic recombination and selection of appropriate ts mutants we shall segregate influenza virus polypeptides for discrete analysis of their composition, antigenicity, structure and function. Special emphasis will be placed on studies of the viral neuraminidase for which variation and amount per virion (genetic dimorphism) and absence of function (in ts mutants) has been discovered. Other studies are planned for approaching the problem of antigenic variation by study of antibody fractions eluted from specific immuno-absorption columns to which isolated polypeptide antigens have been attached. Definition and analysis of mutant complementation and recombination groups will be continued. As a specific practical problem, we shall investigate the nature of the gene(s) associated with high yield in vaccine strains of virus.